Accelerating growth of the world's population, combined with improved standards of living throughout the world, have greatly increased demand for all types of mineral products. At the same time, there have been attempts to shift to alternate sources of energy such as to use steam or water at elevated temperatures in situ for driving compressors and the like. Such geothermal reservoirs are likewise being sought for the same reasons described above and are usually in association with deposits which can be designated as "marker rocks". Unfortunately the contrast between physical properties of economic ore minerals and country or host rock surrounding them are not well defined by conventional surface exploration techniques. In zones of interest, whether an anomaly of interest is from a valuable ore, mineral, etc., or from some other associated rock material having no economic importance, is a most difficult question to answer. This is primarily due to the fact that ore, economic mineral and marker rock deposition are under cover and cannot be observed at the earth's surface.
In oil and gas exploration, seismic refraction shooting has been well known and practiced for decades. But because resolution of events is limited in the vertical direction to shallow structures, crews performing refraction shooting have not used arrays having severely overlapping inline positions. Additionally applicability in the exploration sense of such a refraction technique, say, for discovery of new deposits of ore, marker rock and economic minerals, did not exist. Heretofore, in such refraction shooting, as reported in the book, "Introduction To Geophysical Prospecting", M. B. Dobrin, 2nd Ed., McGraw-Hill, 1960, the detector positions are usually designated X.sub.1, X.sub.2 . . . X.sub.n, with the shot point and detector positions being positioned to provide end-shooting sequences only. Successive shots at uniform or almost uniform intervals, adjacent to the ends of detector spreads, say, adjacent to the near detector position X.sub.1 and the far detector position X.sub.n, provide source waves. Then the detector spread is advanced; its new end position X.sub.1 ' becomes superimposed on the X.sub.n position of the prior spread. In that way, provision can be made for a "tie point" from refraction record to refraction record but not for systematically associating at least two traces with each inline position along the line of survey.